Circle Length Calculator
Enter a circle's radius, diameter, or circumference (its length) to convert between all three instantly.
Circle Length Calculator
"Circle length" is another name for a circle's circumference — the total distance around its edge. Our Circle Length Calculator converts freely between radius, diameter, and circumference, so whichever measurement you have, you instantly get the other two.
What Is a Circle's Length?
If you were to trace a circle's edge with a piece of string and then straighten that string out, its length would be the circle's circumference — its "length." It depends only on the circle's radius or diameter and the constant π (approximately 3.1416).
Conversion Formulas
From Diameter: Length = πd
From Circumference: r = Length ÷ (2π), d = Length ÷ π
Example Calculations
From Radius: r = 5
Length = 2 × π × 5 ≈ 31.42
✓ Length ≈ 31.42, Diameter = 10
From Diameter: d = 10
Length = π × 10 ≈ 31.42
✓ Length ≈ 31.42, Radius = 5
From Circumference: Length = 31.42
r = 31.42 ÷ (2π) ≈ 5, d = 31.42 ÷ π ≈ 10
✓ Radius ≈ 5, Diameter ≈ 10
Features of Our Circle Length Calculator
Who Can Use This Calculator?
👉 Try our Circle Length Calculator to convert between radius, diameter, and circumference in seconds.